Ignition device for restraint means in a vehicle

ABSTRACT

A firing device, in which electrostatic chargings do not lead to an unintentional triggering of the firing element, is composed of a module housing in which a firing element and a circuit means arrangement are arranged, and which has terminal posts that, on the one side, are contacted to the circuit arrangement, and on the other side, are brought out from the module housing for the connection to a plug connector. The firing device includes at least one conductive member that is contacted to the firing capsule and that has a defined distance to the individual terminal posts, such that, in response to an electrical charging, a voltage sparkover occurs between the terminal posts and the conductive member.

FIELD OF THE INVENTION

The present invention relates to a firing device for restraint means ina vehicle, at least one firing element, surrounded by a conductivecapsule, and circuit means—preferably for the energy supply, fortriggering and/or diagnosis of the firing element—being accommodated ina common module housing, and the module housing being provided withterminal posts which, one the one side, are contacted to the circuitmeans, and on the other side, are brought out from the module housingfor connection to a plug connector.

BACKGROUND INFORMATION

A firing device is described in German Patent No. 196 10 799. This knownfiring device is conceived such that it has the smallest possible outerdimensions compared to firing devices used till now, so that, forexample, it can even be accommodated in the steering wheel of a vehicle.Namely, heretofore the firing element and an ignition power module,which contained circuitry for energy supply, for triggering and/ordiagnosis of the firing element, were accommodated in separate modulescontactable to each other via connectors. According to German Patent No.196 10 799, besides a firing element generating the thermal energy forigniting an ignition mixture, also arranged in a module housing arecircuit elements, for instance, for the energy supply, the triggeringand/or diagnosis of the firing element. Located in the module housing,below the firing element, is a rectangular-shaped member in whichcontact pins for the firing element are integrated, and on whosesidewalls circuit elements are applied. The rectangular-shaped member isused both for fixing contact pins for the firing element in place, aswell as for positioning terminal posts which are brought out from themodule housing for contacting to a plug connector.

When handling the firing device prior to or during installation in amotor vehicle, an electrostatic charging can occur within the modulehousing, which means a disruptive discharge voltage can develop that issufficient to trigger the firing element. In the same way, electrostaticchargings in the firing device are possible when it is already installedin a vehicle. Therefore, an object of the present invention is toprovide a firing device which prevents an unintentional triggering ofthe firing element as a result of electrostatic charging.

SUMMARY OF THE INVENTION

According to the present invention, present in the module housing is atleast one conductive member, contacted to the firing capsule, which hasa defined distance to the individual terminal posts, such that inresponse to an electrostatic charging, a voltage sparkover occursbetween the terminal posts and the conductive member. The terminalposts, together with the conductive member, form a spark gap over thedefined distance, via which a discharge occurs when the charge exceeds acertain value. The charge is thereby prevented from discharging directlyto the firing element, and there causing an unintentional triggering.

Accordingly, the conductive member is mounted on a base that fixes theterminal posts in position. The conductive member can be contacted tothe firing capsule either by the conductive member having a cut-out formounting the firing capsule, or by providing the firing capsule with asleeve which is able to be placed over the conductive member. In thiscontext, the conductive member can be a metal ring that rests on thesubstrate and has a collar forming an angle, over which the sleeve ofthe firing capsule can be placed.

Circuit means can be arranged on a substrate, a spring element restingon the substrate producing an electrical connection between the circuitmeans on the substrate and contact pins of the firing element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section through a firing device of a firsttype.

FIG. 1a shows a cross-section A—A through the firing device.

FIG. 1b shows a cross-section B—B through the firing device.

FIG. 2 shows a longitudinal section through a firing device of a secondtype.

FIG. 3 shows a longitudinal section through a firing device of a thirdtype.

DETAILED DESCRIPTION

The firing device shown as a longitudinal section in FIG. 1 isconstructed as follows: Situated in the lower part is a base 1 in whicha plurality of terminal posts 2 are fixed in position. Base 1 is madeeither of a plastic or a metal. In a metal base 1, terminal posts 2 mustbe fixed in position in an insulated manner, for example, by a glassmelt. Terminal posts 2 extend on one side into the interior of themodule housing of the firing device, and on the other side, project outof the module housing for the connection, for example, to a busconnector. Triggering signals, for instance, or other data aretransmitted via terminal posts 2 to the firing device from a centralcontrol unit connected to a bus line.

Base 1 is used as a mounting support for a substrate 3, on whose upperand/or lower side a plurality of circuit elements 4 are arranged. Thesecircuit elements 4 are, for example, SMD-components or ASIC's inflip-chip technology. Circuit elements 4 are preferably energy-supplycircuits or circuits for triggering and/or diagnosing a firing elementlocated in the module housing, it being possible to see capsule 5surrounding the firing element and contact pins 6 and 7 brought out fromit in FIG. 1. The firing element itself shall not be further describedhere, since it can be designed according to the related art (e.g. GermanPatent No. 196 10 799). In the simplest case, it is a resistance wire towhich a current can be supplied via contact pins 6 and 7. Located withinfiring capsule 5 is a firing charge which is fired in response tocurrent flow via contact pins 6 and 7. In the exemplary embodimentshown, a further encapsulated firing charge 8 is disposed above firingcapsule 5. This further firing charge 8 is necessary when, for example,the firing device is intended to be used in a seat-belt tightener.Otherwise, however, the one firing charge provided in firing capsule 5also suffices.

An electrical connection between contact pins 6 and 7 of firing element5, and circuit elements 4 on substrate 3 is effected via a springelement 9 that rests on substrate 3, is contacted there to printedcircuit traces and has elastic contact tabs 10 and 11 which touchcontact pins 6 and 7 of firing element 5. A cross-section A—A, shown inFIG. 1a, clarifies the embodiment of spring element 9. Spring element 9is made of an insulating plastic framework which, in a clamp-likemanner, embraces terminal posts 2 that protrude through substrate 3 andare contacted to printed circuit traces on substrate 3, and in thismanner is retained in a fixed position. Contact tabs 10 and 11 are hungin the plastic framework of spring element 9, the contact tabs havingsuch a distance with respect to terminal posts 2 that a voltagesparkover cannot occur between terminal posts 2 and contact tabs 10 and11 in the event of an electrostatic charging of the firing device.

As FIG. 1 shows, a conductive member 12 is disposed on the edge of base1 in the interior of the module housing. This conductive member 12 isused as retainer for firing capsule 5. Conductive member 12 iselectroconductively contacted to firing capsule 5 and has an opening 13through which contact pins 6 and 7 of firing element 5 extend to contacttabs 10 and 11 of spring element 9. Cross-section B—B, shown in FIG. 1b,shows clearly that, extending around opening 13, through which springelement 9 is visible in FIG. 1b, is an edge 14 of conductive member 12,upon which firing capsule 5 rests. Firing capsule 5 can be fixed inposition in conductive member 12 by soldering, welding, cementing orpress-fitting.

FIG. 1 shows that firing capsule 5, conductive member 12 and base 1 areenclosed by a plastic extrusion coat 15. Finally, located below base 1is also a (socket 16. A casing 17 (made, for example, of aluminum)encloses socket 16, plastic extrusion coat 15 and further firing charge8, resulting overall therefore in a closed module housing.

When installing the firing device in a vehicle, an electrostaticcharging of the firing device can occur, because of which, currents ofsuch magnitude may flow via contact pins 6 and 7 through the firingelement that an unwanted firing comes about. To rule out suchunintentional firings, means are provided in the firing device whichprevent electrostatic charges from discharging via contact pins 6 and 7through the firing element and possibly triggering it. These meansinclude conductive member 12, with respect to which terminal posts 2,via which electrostatic charges can flow from the outside into thefiring device, have a defined distance a (see FIGS. 1, 1 b). Terminalposts 2, which extend into opening 13 of conductive member 12 and, in sodoing, maintain distance a with respect to conductive member 12, form,together with conductive member 12, a spark gap via which anelectrostatic charge can be reduced through a voltage sparkover, withoutat the same time a current flowing via firing element 5. Distance abetween terminal posts 2 and conductive member 12 is to be especiallyselected in such a way that, in response to voltages which could lead toan unintentional firing, a sparkover occurs. Thus, electricallyconductive member 12 has not only the function of a mounting support forfiring element 5, but is also used as a charge bleeder to protect firingelement 5 from unintentional firings.

FIG. 2 shows a second specific embodiment of a firing device. It againhas a base 20 in which terminal posts 21 are fixed in position. In thiscase, base 20 is a metal base in which terminal posts 21 are fixed inbore holes in an insulating manner by a glass melt 22. Resting on base20 is a metal ring 23 which has a collar 24 forming an angle downwardover the edge of base 20. An insulating body 25 is inserted betweenmetal base 20 and a substrate 26 which is fixed in position withterminal posts 21 by soldering or cementing. The upper and lower sidesof substrate 26 are equipped with circuit elements 27. A spring element28 mounted on substrate 26 is contacted on the one hand to printedcircuit traces on substrate 26, and on the other hand, has contact tabs29 and 30 which produce an electrical connection between circuitelements 27 on substrate 26 and contact pins 31 and 32 of a firingelement. As already described in connection with FIG. 1, the firingelement is accommodated, together with a firing charge, in a capsule 33.Firing capsule 33 is provided with a sleeve 34, projecting beyondcontact pins 31 and 33, which can be placed over angled collar 24 ofmetal ring 23. Sleeve 34 of firing capsule 33 is fixed in position oncollar 24 of metal ring 23 by soldering, welding or cementing. Due tosleeve 34 of firing capsule 33, the necessary space is obtained formounting circuit elements 27, and at the same time, firing capsule 33forms the outer casing of the entire firing device.

Like conductive member 12 in the exemplary embodiment of FIG. 1, metalring 23 is used here as a mounting support for firing capsule 33, and atthe same time for the discharge of electrostatic charge. Terminal posts21 are led past metal ring 23 at a distance a, so that a spark gap isformed between terminal posts 21 and metal ring 23.

The exemplary embodiment of a firing device shown in FIG. 3 differs fromthat in FIG. 2 merely in that base 20 is made of an insulating plastic,which is why it is possible to dispense with insulating medium betweenbase 20 and substrate 26. In addition, metal ring 23 has a collar 35forming an angle upward, over which sleeve 34 of firing element 33 isplaced. Otherwise, this metal ring 23 has the same function as a sparkgap, as has already been described in the exemplary embodiment of FIG.2. A plastic extrusion coat 36 encloses sleeve 34 of firing capsule 33with base 20.

What is claimed is:
 1. A firing device for a restraint device in avehicle, comprising: a conductive firing capsule including contact pins;a substrate; a circuit arrangement situated on the substrate; a commonmodule housing accommodating the circuit arrangement, the module housingincluding terminal posts, the terminal posts having a first sidecontacting the circuit arrangement and having a second side extendingfrom the module housing; at least one conductive member contacting thefiring capsule, the at least one conductive member having a defineddistance to the terminal posts such that, in response to anelectrostatic charging, a voltage sparkover occurs between the terminalposts and the at least one conductive member; and at least one contacttab coupled to a spring element situated on the substrate, wherein theat least one contact tab produces an electrical connection between thecircuit arrangement and the contact pins.
 2. The firing device accordingto claim 1, wherein the circuit arrangement performs at least one of thefollowing: supplies energy, triggers the firing capsule, and diagnosesthe firing capsule.
 3. The firing device according to claim 1, furthercomprising a base for fixing the terminal posts in position, the atleast one conductive member being mounted on the base, the at least oneconductive member having a cut-out for mounting the firing capsule. 4.The firing device according to claim 1, further comprising a base forthe terminal posts in position the at least one conductive member beingmounted on the base, the firing capsule having a sleeve capable of beingplaced over the at least one conductive member.
 5. The firing deviceaccording to claim 4, wherein the at least one conductive memberincludes a metal ring situated on the base, the metal ring having acollar forming an angle, the sleeve of the firing capsule being capableof being placed over the collar.